Process for the purification of air



Patented Aug. 1 5,

v 7 I 1322,13? rnoonss roa'rnn runrr os'r or or All:

? Walter Ziseh,Frankfort-on-the-Main,-Ge1*many,' assignor, by mesne assignments, to. E. I. du

Pont de Nemours of Delaware and Company, a Corporation No' Drawing. Application: April 29,1929, Serial No; 356,892, and in GermanyApril 21-, 1928 3 Claims,

This, invention has to do with exchange masses,

that is, those which purify and renew exhaled air, such as that occurring in closed spaces or in breathing apparatus, by exchanging oxygen gas for impurities such as carbon dioxide and excesl sive quantities of moisture.

I have now found that masses consisting of, or containing alkali metal trioxides such as sodium trioxide, or mixtures of these trioxides, can be used with good results for purifying exhaled air.

The alkali trioxides can be prepared in any known manner. However, exchange masses .of exceptional activity containing alkali metal trioxide, for example, sodium trioxides can be prepared by reacting equi-molecular parts of natryl l5 hydroxide and sodium peroxide by mixing them together, and if necessary heating them, to cause the following reaction:

.9 The reaction between the two substances very often assumes explosive character. 'It is therefore advisable to modify the speed of the reaction by admixing substances which do not take part in the reaction. Such substances may be in- V ert materials such as sodium chloride, or substances favoring the absorption of. thecarbon di-' If one permits carbon dioxide or gas mixtures containing carbon dioxide, such as exhaled air from the lungs; to pass through or over sodium l5 .trioxide' or mixtures containing sodium trioxides,

there is a regular current of oxygen set free.

This evolution of oxygen results from action of carbon dioxide on the productand is enhanced by the water vapor which is always present in ex-' 19 haled air, and onaccount of the heatwhichis produced when this water is taken up' by the favored. a

I prefer to convert the exchange masses into i a solid or porous form by adding alkali hydroxide to the finely pulverized mixture of alkali metal hydrogen perioxide and alkali metal peroxide, using pressure to briquette the mass, and applying heat to the molded pieces inorder to con- 59 vert the material to the desired product. The

forming or molding of the mass can also be car- 'ried out during or after the heating process. When alkali metal hydrogen peroxide is mixed with alkali metal peroxide even in the presence 5. of diluting agents such as alkali metal peroxide hydgroscopic mass, the evolution of oxygen is exceptional porosity and increased efiiciency for haled air. Such catalysts are, for example,

the temperature in. the mixed mass. gradually rises and may go up as far as 150 to zoo cenngrade whilst the mass is converted into alkali trioxide. The conversion may be gauged by the amount of gaseous oxygen being liberated as soon as small fractions of the mass'are brought in touch'with water. If the amount of diluentsis rather great and, in consequence, the rate of conversion becomes sluggish the reaction may be assisted by cautiously applying heat'to the mass, taking care that the temperature does not exceed materially 150 to 200 0. Any rise above this 7 limit is connected with avoidable loss of oxygen.

. The molded masses can be used directly in breathing apparatus, or one can increase their surface and therefore increase the possibility that 79 the gas will be brought into close contact with the exchange mass. This can be done by giving the molded pieces a wave-like serrated form or making them sufficiently thin that they will be completely utilized and that 'no unused material 15 will remain in the interior parts of the mass.

. The molded pieces can also be madefsmall enough that "a breathing apparatus can be filled with the same. If it is desired, one can produce large molded pieces, and after heating these in order to so 7 a cause the desired reaction and then cooling, the

'pieces'may be broken up into granular form and used. a r

'During the process of sifting out grains of the desired size fines are produced' These may 8 S V be made up into briquettes or can be added to themixture of the substances'preferably before molding or converting them by means .of heat. In this manner, masses are produced having-an liberating oxygen.

It has been found advantageous to have present in thegexchange, masses, catalysts facilitating the liberation of oxygen in the presence of exoxides'or other compounds of manganese, cobalt, copper and the like. These catalytic compounds can be incorporated into the mass at anytime during the process of preparation. In many cases it is sufiicient to dust the mass with the powdered oxidesor their compounds. For example, copper sulphate may be used in place of copper oxide. The oxides can'even be produced in the mass, itself by mixing the latter with the correspondingly finely divided metal which is changed to oxide during the step of heating.

Example 1.5.90 kilograms natryl hydroxide are added gradually to 10.0 kilograms sodium peroxide, mixing the two substances very thoroughly if necessary with grinding, taking care that the temperature does not rise too suddenly. After allowing the mixture to stand for some short time, gentle heat is applied-sothat the temperaturefin the mass does not exceed 1150 to 200 C. After keeping it for sometime the mass is allowed to cool, is then dusted'with manganese peroxide powder and is ready for use.

Example 2.5.9 kilograms natryl hydroxide are added in small portions to'a mixture of 4.0 kilograms sodium hydroxide and 7.8 kilograms sodium peroxide having been ground-together previously. The mixture isground thoroughly and molded in a hydraulic press; The shaped pieces are heated gradually-toabout 120 C. and. kept at this heat for sometime. The 'molded pieces after cooling may be used as such in the breathing apparatus or they may be broken up intogranular form. The fines are sifted off and usedffor admixing to the next charge as. diluent.

into contact withwater,

The sodium trioxide obtained in this way has a yellowish color and gives 01f at once its contents of oxygen in gaseous form when brought What I claimisj: V f 1. In a method for renewing exhaled air, the

step which comprises bringing said air into contact with a mixture of an alkali metal trioxide um hydroxide with a catalyst capable of promoting the liberation of oxygen from said trioxide in the presence of breathed air. I WALTER; ZISC'H. 

